False Gossip, I need help

So I have this friend who told me he heard a rumor about me sending nudes.(I don’t and would never) the guy who made this up apparently showed him a picture of a Vagi...which was not mine cause I wouldn’t take a picture of down-there or of myself naked ever . My friend told the guy to stop saying it or he would hurt him. But now I’m afraid about having a rumor like that going around. And I haven’t told my mom cause it would make things awkward and to be honest I just want to forget about it but if the rumor comes up again and I need to tell my mom the fact that I didn’t tell her in the first place may make me seem guilty. And my friend won’t tell me who said it cause he promised he wouldn’t.What should I do and has something like this ever happened to any of you before?